1. Field of the Invention
This invention pertains to portable hazard detectors such as detectors for smoke, carbon monoxide or other environmental hazards. More particularly, this invention pertains to a hazard detector with a theft prevention feature.
2. Description of the Prior Art
Hazard detectors are well known for detecting hazards such as fire, smoke or carbon monoxide or the like. An example of such is found in U.S. Pat. No. 4,812,827 to Scripps, dated Mar. 14, 1998. The '827 patent describes a wall mounted smoke detector which is retained in place solely by reason of male electrical prongs received within a standard female electrical receptacle. The '827 patent teaches a battery contained within the smoke detector which acts as a back-up in the event the power system to the female receptacle fails. The apparatus of the '827 patent also includes a charger mechanism for charging the battery while the unit is plugged into a wall outlet.
Other examples of smoke detectors include U.S. Pat. No., 5,574,436 to Sisselman et al., dated Nov. 12, 1996 which includes a primary power source (such as a building power supply) and a battery. The apparatus sounds an alarm if loss of the primary source is detected. The supplementary power source is substantially non-removable by a consumer. Specifically, the '436 patent teaches a supplementary power source in the form of a battery which is completely enclosed in plastic and, thus, rendered substantially non-removable by a consumer in the absence of using physical force to alter the smoke detector's circuitry or housing. Other examples of such smoke detectors include U.S. Pat. Nos. 5,969,437; 4,893,324; 6,492,907; 4,779,078; 4,419,658; and 4,380,760.
Wall mounted smoke detectors such as that described in the aforementioned U.S. Pat. No. 4,812,827 can be made at reasonable prices to encourage their use in structures not otherwise provided with smoke detectors. As a result, low cost smoke detectors may be applied to retrofit existing structures to provide the safety benefits of smoke detection. Landlords or other non-resident owners may elect to put such devices in apartments. Pre-existing hotels and motels may elect to put such devices into guest rooms.
Unfortunately, individuals may elect to tamper with or steal portable smoke detectors. For example a hotel guest may steal a smoke detector where it is not physically secured to the structure but is only plugged into a wall outlet. In addition to stealing the smoke detector, individuals might elect to remove the smoke detector to obtain access to a battery compartment and steal the battery.
Anti-theft and anti-tampering devices are known. The aforementioned U.S. Pat. No. 5,574,436 attempts to prevent unauthorized removal of the battery by encasing a battery in plastic to prevent removal of a battery from a smoke detector. A number of other devices are known for preventing unauthorized removal of electronic equipment. For example U.S. Pat. No. 5,767,771 to Lamont, dated Jun. 16, 1998 describes disabling a computer if it is disconnected from a system and includes tamper detection circuitry. U.S. Pat. No. 5,525,965 to Liebenthal, dated Jun. 11, 1996 teaches an apparatus to sound an alarm in the event an attached appliance is unplugged. Similar apparatus are shown in U.S. Pat. No. 3,484,775 to Cline, dated Dec. 16, 1996; U.S. Pat. No. 3,618,065 to Trip, dated Nov. 2, 1971; U.S. Pat. No. 4,300,130 to Fotheringham et al., dated Nov. 10, 1981 and U.S. Pat. No. 4,736,195 to McMurtry et al., dated Apr. 5, 1988 as well as U.S. Pat. No. 5,818,338 to Ferraro, dated Oct. 6, 1998. It is an object of the present invention to provide a portable smoke detector which may be plugged into a wall and which will sound an alarm in the event it is removed from a wall outlet.